Modern electronic devices such as notebook computers comprise a variety of memories to store information. Memory circuits include two major categories. One is volatile memories, the other is non-volatile memories. Volatile memories include random access memory (RAM), which can be further divided into two sub-categories, static random access memory (SRAM) and dynamic random access memory (DRAM). Both SRAM and DRAM are volatile because they will lose the information they store when they are not powered. On the other hand, non-volatile memories can keep data stored on them without power. Non-volatile memories include a variety of sub-categories, such as read-only-memory (ROM), electrically erasable programmable read-only memory (EEPROM), and flash memory.
ROM devices are a kind of memory where, in normal system operation, the memory is read but not changed. Usually, ROM devices are used for high volume controlled applications such as the set of instructions that is needed to make the computer system ready for use when its power is turned on. These instructions are startup instructions, commonly found in a ROM device.
A ROM device comprises an array of storage cells. A sequence of digital data comprising ones and zeros are stored in the array of storage cells of the ROM device. Each storage cell is connected to a bit line and a word line, and stores a zero or an one. There may be different ways to store the ones and zeros in the storage cells of the ROM device. Current technology for ROM devices may use an encoding of the ones and zeros into the storage cells resulting in a large number of storage cells, a large storage line capacitance, and high power consumptions. New encoding and implementation of digital information of ones and zeros into the storage cells for the ROM device is needed.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.